The present invention relates to frequency generators. Prior art frequency generators have tried various approaches to provide a large number of frequencies over a wide bandwidth with good resolution and a rapid switching speed. This type of frequency generator is particularly useful in radar applications involving frequency hopping and Doppler signals.
One approach is shown in U.S. Pat. No. 3,956,703. This construction utilizes a phase locked loop. The patent construction provides accuracy of frequencies with fairly good resolution but is too slow to accomplish rapid switching. This construction cannot accomplish close channel spacing. Channel spacing of twenty-five kilohertz is recited in the reference. The patentee obtains a limited number of frequencies. The switching speed varies in the patented device depending upon the closeness of the channels.
U.S. Pat. No. 4,105,949 discloses another approach to frequency generators. This is a cumbersome construction in that it requires a large number of filters. Hundreds of filters are required for generating a large number of frequencies. There is also a noise problem with such an arrangement. This device lacks good resolution. The patented device uses comb filters and cannot obtain the switching speed and desired resolution for an application such as radar. This construction is limited in bandwidth.